High frequency coil for electric induction furnaces



Aug. 11, 1931. e. E. TAYLOR 1,818,107

HIGH FREQUENCY COIL FOR ELECTRIC INDUCTION FURNACES filed July 5, 1928 L? if Patented Augrll, 1931 UNITED [STATES- PATENT. OFFICE GEORGE EDWARD TAYLOR, OF LONDON, ENGLAND, ASSIGNOR 1'0 AJAX ELECTBO- C CORPORATION, OF TRENTON, NEW JERSEY, A CORPORATION OF NEW HIGH FREQUENCY OOH. FOB ELECTRIC INDUO'IION FURNACES Application filed July 5, 1928, Serial No. 290,400, and in Great Britain December 7, 1927.

My invention relates to induction electric aces in which the inductor is applied in a single layer about the molten metal and requires special cooling accommodation.

5 In electric induction furnaces energized by high frequency currents, the losses in the primary furnace coil maybe a considerable prortion of the total energy applied to the coil. t is therefore of great importance that the coil should be designed to reduce these losses to a When conductors in the form of flat copgf nstrips, such as are generally used in the ace coil, carry high frequency currents,

the useful radial width is limited by the electrical phenomenon known as skin effect, and its resistance cannot be reduced by increasing the width of the conductor beyond a certain limit. It is also found that when the conductors'are in the form of a cylindrical helix; the distribution of the current is not uniform over the radial width of the conductor shown as edgewise wound, but is displaced towards the inner diameter of the helix.

It is therefore necessary that to reduce the resistance of a given coil the axial depth of the co per in the turns should be a maximum an the insulating and cooling space between the turns a minimum. If, however,

' so the axial depth of the copper is large, eddy currents are induced in it which may attain a considerable magnitude and cause an appreciable loss. I

The object of the invention is to construct 86 a coil in such a manner as to reduce the various losses to a minimum and to rovide means for efiectively taking away t e heat which maly be generated in the coil.

igure 1 is a fragmentary cross section of a 40 furnace to which my invention is applied. I Figures 2-5 illustrate examples of cross sections of conductors according to the invention. v

1 is intended merely to show one at setting in which my invention appears in which I have showna crucible 1, separated V ingbeyond the other conductors. T is construction enables the heat enerated in the coil to be readily transferre to the surroundin atmosphere.

he parallel conductors may be separated by a sllght coating of insulating varnish or strips 0 insulator in order to minimize the eddy current losses. Where used this varnish or insulating coating will be represented by division lines between the parallel conductors of the same turn.

Figure 3 is similar to Fi ductor consists of two ro ecting stri s a, a andthree strips 12', b, a of less radia width. The copper or othermetallic strips may be replaced y cables or tubes.

When it is desired to cool the coil by the re 1, but the conflow of a cooling 1i uid or gas, the projectin conductors may formed as a tube.

igure 4 shows an example of this construction in which the radiall extended conductor c is formed. as a tube w ich .is flattened at the part interposed between the strip conand two tubes 0', c are shown.

What I claim as new anddes'ireto secure by Letters Patent is 1. In an electric inductor furnace, an inductor coil comprising in each turn a tubular member flattened'in one part to provide a.

solid radially inner conducting portion and a radially exterior hollow part to receive a 5 cooling liquid.

2. An inductor coil comprising a plurality of adjacently located current-traversed conductors, and artificial cooling means coextensive therewith and embodymg a metal element having a fluid-traversed tubular portion and a fin portion operatively engaging the conductors.

GEORGE EDWARD TAYLOR. 

